Cooling apparatus

ABSTRACT

A dewar surrounding a cold region and attached to a radiating surface adapted to be directed toward dark space, whereby the dewar insulates the cold region from surrounding heat sources in an atmospheric environment, and it conducts heat away from the cold region to the radiating surface in a space environment.

Unlted States Patent 1191 I 3,732,421

Kunimoto et al. I 1 May 8, 1973 54] COOLING APPARATUS 3,620,186 11 1971King ..250/83.3 1-1 [75] Inventors. Wallace Kunimoto, Goleta; 3,529,1649/1970 Komatsubara et al... .....250/83.3 H Joseph Buller, Santa Barbara3,602,714 8/1971 Farmer ..250/83.3 1-1 both of Calif. PrimaryExaminer-Archie R. Borchelt [73] Asslgnee' g i t il Research CenterAssistant ExaminerDavis L. Willis 0 e a1 Att0rneyW. H. MacAllister, Jr.and Ernest L. Brown [22] Filed: May 20, 1971 21 Appl. No.: 145,363 [571ABSTRACT A dewar surrounding a cold region and attached to a [52] Cl250/83 R 250/333 H, 165/185 radiating surface adapted to be directedtoward dark [51] Int. Cl ..(;0111/24 p whereby the dewar insulates thecold region [58] Field of Search ..250/83.3 H; 165/185, from surroundingheat sources in an atmospheric en- 165/133 vironment, and it conductsheat away from the cold region to the radiating surface in a spaceenvironment. [56] References Cited 10 Claims, 1 Drawing Figure UNITEDSTATES PATENTS 3,422,886 l/l969 Buller ..l65/l33 X] I L r 5 ,/26 28 1 i1 ll l i a2 [/1 I I// 1 l f l 3s 3s 10 a4 PATENTEB HAY 8 1915 Wallace Y.Kunimofo, Joseph S. Buller,

INVENTORS.

ATTORNEY.

COOLING APPARATUS BACKGROUND OF THE INVENTION The invention is directedto apparatus adapted to maintain a radiation detector in a cold regionat its optimum cryogenic operating temperature.

It is well known that radiation detectors have great utility in scanningthe earth from an orbit position.

Most of the detectors now being used require, for efficient operation,that they be maintained at an ambient temperature in the cryogenicrange, for example, below 77 K. Characteristically, prior art detectorcoolers use stored cryogens such as that shown and described in U.S.Pat. No. 3,457,730 which issued July 29, 1969 to R. L. Berry, et. al.,for a Throttling Valve Employing the Joule-Thomson Effect which isassigned to Hughes Aircraft Company, the Assignee of the presentapplication.

The use of a stored cryogen for cooling a radiation detector in spaceenvironment has the disadvantages of relatively short service life.Therefore, apparatus, such as the Radiation Cooler for use in Space of,U.S. Pat. No. 3,422,886 which issued Jan. 21, 1969 to J. S. Buller andwhich is assigned to Hughes Aircraft Company, is typically used.

Unfortunately, testing of the apparatus using a radiation coolerrequires that the equipment be placed in a vacuum and cooled byradiation while it is on the ground.

To avoid the necessity of using a vacuum during testing of the apparatusand prior to launch of the apparatus, the structure of this inventionwas conceived.

In the device contemplated by this invention, the radiation detector iscooled, while on the ground, by a cryostat surrounded by a dewar. Thedewar insulates the detector from the surrounding heat of theatmosphere.

In a space environment, after the apparatus is launched, the cryostat isno longer connected and apparatus such as that shown and described inthe abovementioned U.S. Pat. No. 3,422,886 is used to cool the detector.The dewar, however, in the embodiment of this invention is not removed,but rather is attached to a radiating surface, whereby, in space, thewall of the SUMMARY In order to aid in the understanding of thisinvention it can be stated that in essentially summary form that it isdirected to a cooling apparatus which comprises a dewar having a wallfor attachment of a device to be cooled on a cold region thereof, thecold region being coolable by heat transfer through the wall to acoolingmeans on the other side of the wall, or being coolable by heat transferalong the wall to a radiation surface attached to the wall.

It is therefore an object of this invention to use a dewar forinsulating a cold region when the surrounding atmosphere is at asubstantially higher temperature than the region to be cooled and to usethe dewar as a conductor to a radiating surface, pointed toward the darkof space when the dark of space is cooler than the cold region.

It is another object of this invention to maintain a radiation sensor atcryogenic temperatures.

It is still another object of this invention to provide a method forcooling a cold region, and particularly when a radiation detector is insaid cold region.

BRIEF DESCRIPTION OF THE DRAWINGS Other objects will become apparentfrom the following description, taken in connection with theaccompanying drawings, in which the only drawing is a view, partly insection, of the apparatus of this invention, schematically connected toa source of gas for the cryostat.

DETAILED DESCRIPTION OF THE INVENTION A radiation sensor 10, such as ainfrared sensor, is maintained at a cryogenic temperature by theapparatus of this invention.

In a preferred embodiment the sensor device 10 is positioned on a coldregion on the end of a cold finger 12. Internal of the cold finger 12 isa plurality of coils such as the coil 14 attached, through a filter 16and a control valve 18, to a source 20 of a gas such as nitrogen.

The cold finger 12 also forms the inner wall of a dewar. The outer wallof the dewar is shown at 22. Between the walls 12 and 22 a vacuum ismaintained.

The inner and outer walls 12 and 22 of the dewar are conductivelyconnected to a radiating member 24. The radiating member 24 preferablyhas a black outer surface, whereby heat is radiated into space when saidsurface is pointed at free space or a region colder than the radiator.

The remainder of the structure such as the member 26 and the member 28may be supported, for example, by means, such as wires 30 and 32, in thefashion shown, described and claimed in the above-mentioned U.S. Pat.No. 3,422,886. Member 26 corresponds to the second radiation stage ofthat patent.

Windows 34, 36, and 38 allow the sensor 10 to receive radiation. To thatend, the windows may be made of special material to allow infraredradiation to pass therethrough.

Prior to launch, or during'tests of the apparatus, upon the ground or inan atmosphere, with sensor 10, for example, at 77 K and the outeratmosphere, for example, at 300 K the heat conduction from the outeratmosphere into the detector 10 is on the order of one and one-halfwatts. The one and one-half watts of power are removed by the gas in thecryostat coils 14.

During this pre-launch phase, the sensor 10 can be cooled by othermeans. For example, liquid nitrogen may be placed in contact with thesensor 10 or a heat engine may be used. Radiation, however, is usuallyinsufficient because of the amount of heat which must be removed.

In a space environment, the wall 12 acts as a conductor of heat. Withthe surface of the radiator 24 pointed toward the darkness of space, thetemperature difference between the detector 10 and free space is on theorder of 025 K, and the heat conduction of the wall 12 is on the orderof 0.001 watts. The surface of radiator 24 is preferably black to thelong wave infrared associated with heat radiation although it may evenbe visibly white.

Typically, the wall 12 is made of copper and nickel alloy. A typicalwall thickness of the wall 12 is 0.015 inches, a typical length of thewall 12 between the detector land the radiator 24 is 1.75 inches, and atypical diameter of the wall '12 is 0.204 inches.

In addition to the functions just mentioned, the dewar prevents moisturefrom condensing in the region of the detector 10, whereby dust and otherforeign particles are prevented from adhering to the detector andthereby ruining the detector.

Thus, the combination of this invention is particularly designed for amultiple use. That is, the dewar acts as an insulator where the outsidetemperature is relatively high and as a conductor to a radiator when theradiator is looking toward a cold sport in space and the outsidetemperature is relatively low.

Although the invention has been described in detail above, it is notintended that the invention shall be limited by that description butonly in accordance with that description taken in combination with theappended claims. a

What is claimed is:

1. A cooling apparatus comprising:

a dewar surrounding a cold region;

a wall forming a portion of a cold finger and attached to said dewar;

said cold region being on said wall and being for attachment thereto ofa device to be cooled;

means associated with said wall for cooling said wall for conductivecooling of the cold region by heat conduction through said wall; and

radiating surfaces attached to said wall and conductively connected tosaid cold region for cooling the cold region by conduction along saidwall.

2. Apparatus as recited in claim 1 in which said radiating surfaces areblack to infrared radiation at long wavelengths.

3. Apparatus as recited in claim 1 in which said wall is a wall of saiddewar.

4. Apparatus as recited in claim 3 wherein said means for cooling saidwall is a cryostat, positioned within said dewar, for removing heat fromsaid cold region.

5. Apparatus as recited in claim 4 and further comprising a source ofgas attached to said cryostat and at least a valve between said sourceof gas and said cryostat.

6. Apparatus as recited in claim 5 in which said radiating surface isblack to infrared radiation at long wavelengths.

7. Apparatus as recited in claim 6 and further comprising a radiationdetector attached for thermal communication to said wall in said coldregion.

8. Apparatus as recited in claim 7 wherein said wall is an inner wall ofsaid dewar, said dewar having an outer wall which has a window thereinin the region of said detector for transmitting radiation to bedetected.

9. Apparatus as recited in claim 8 wherein a second stage radiationcooler extends partially around said dewar.

10. Apparatus as recited in claim 9 in which said second stage radiationcooler has a window therein,

positioned to allow radiation to be received by said detector throughsaid windows in said dewar and said radiation cooler.

1. A cooling apparatus comprising: a dewar surrounding a cold region; awall forming a portion of a cold finger and attached to said dewar; saidcold region being on said wall and being for attachment thereto of adevice to be cooled; means associated with said wall for cooling saidwall for conductive cooling of the cold region by heat conductionthrough said wall; and radiating surfaces attached to said wall andconductively connected to said cold region for cooling the cold regionby conduction along said wall.
 2. Apparatus as recited in claim 1 inwhich said radiating surfaces are black to infrared radiation at longwavelengths.
 3. Apparatus as recited in claim 1 in which said wall is awall of said dewar.
 4. Apparatus as recited in claim 3 wherein saidmeans for cooling said wall is a cryostat, positioned within said dewar,for removing heat from said cold region.
 5. Apparatus as recited inclaim 4 and further comprising a source of gas attached to said cryostatand at least a valve between said source of gas and said cryostat. 6.Apparatus as recited in claim 5 in which said radiating surface is blackto infrared radiation at long wavelengths.
 7. Apparatus as recited inclaim 6 and further comprising a radiation detector attached for thermalcommunication to said wall in said cold region.
 8. Apparatus as recitedin claim 7 wherein said wall is an inner wall of said dewar, said dewarhaving an outer wall which has a window therein in the region of saiddetector for transmitting radiation to be detected.
 9. Apparatus asrecited in claim 8 wherein a second stage radiation cooler extendspartially around said dewar.
 10. Apparatus as recited in claim 9 inwhich said second stage radiation cooler has a window therein,positioned to allow radiation to be received by said detector throughsaid windows in said dewar and said radiation cooler.